Serial.available( )

Serial.available( )
Serial.available( )

Arduino’s Serial.available() function examines the Input buffer for data. Readable bytes are returned by this function. This function counts bytes and process data to delete from the serial buffer. The function merely shows how much data is in the buffer that hasn’t been read out. Buffer data can include special characters, quantity of characters, unread data from several devices connected to separate ports, etc. Bytes available to read from the buffer are returned by Serial.available().

Overview of Serial.available( )

Serial.available() returns read-able bytes. The function returns the number of bytes accessible to read after checking. Since available( ) requests a number of bytes, it verifies if they are available. Most messages send a consistent number of bytes, making this a convenient approach to track a message. Note that the buffer has the same number of released bytes and characters. A byte usually represents a character.

 Purpose of Serial.available( )

When you use, Serial.parseFloat(), Serial.readBytes(), Serial.readBytesUntil(), or Serial.parseInt(), the Arduino does not receive any data. The key is that these functions ‘wait for data to arrive’. Using them stops your program and waits for data. You can wait ‘forever’ without data in the buffer. The rest of your program will stop till data arrives. The Serial.available() function. Serial.available() is the initial defense. This should work, follow these steps.

Arduino beginners are trying to understand Serial.available(), which appears in many examples. What does it do and why do you need it? We know the Arduino reference may make basic things look hard for beginners. Fear not—we’ll explain everything in simple terms. You’ll quickly understand Serial.available() and be ready to employ serial communication in your projects. Stay with us as we explain this deceptively easy method and turn those obscure code snippets into working code. Got it!

What Is Serial.available()?

If you’re new to Arduino and serial communication, learn Serial.available(). It lets your Arduino check for serial port data.

When you upload a serial sketch to your Arduino, it opens a virtual serial connection for data transfer between your computer and the Arduino. Serial.available() examines this port for unread computer-to-Arduino traffic.

If there’s no data to read, Serial.available() returns 0.
If data is available, it returns readable bytes.
As an example:

Incoming serial data: int incomingByte = 0.

In void setup(), define Serial.begin(9600) to open the serial port and set the data rate to 9600 bps.

void loop() { if (Serial.available() > 0) { incomingByte =; serial.println(incomingByte);
This basic sketch checks Serial.available() in the loop, reads data with, and publishes it to the serial monitor.

Serial.available() lets your sketch check for serial data without blocking. If no check was made and no data was available, would stall program execution until data came.

In conclusion, Serial.available() lets you efficiently check for serial data in your Arduino project without stopping it. Handy for serial-communication projects! Any questions? Let me know.

When to Use Serial.available()

Serial.available() counts serial buffer bytes for reading. This helps you determine if there are enough bytes to read before reading them.

Say you’re waiting for a sensor to communicate 10 bytes over serial. Something like this:

void loop() { if (Serial.available() >= 10) We have 10 bytes, so read them!
byte sensorData[10]; Serial.readBytes(sensorData, 10); // Use sensorData �
This continuously checks for 10 or more bytes and reads them when data is received. If you read 10 bytes without checking, your code would block while waiting for the rest.

If you’re unsure how many bytes you’ll get, Serial.available() can help. Depending on user input or environmental conditions, a sensor may deliver different amounts of data. You can try this:

void loop() { // Read bytes till timeout unsigned long timeout = millis() + 100; while (millis() < timeout && Serial.available() > 0) { byte b =; // Process the received byte }
As long as bytes arrive via the serial port, this will read and process them for 100ms.

Thus, use Serial.available() when:

Check if enough bytes arrived before reading.
Not knowing how many bytes you’ll get.
You wish to read bytes for a while.
Serial.available() ensures efficient and resilient serial communication in certain instances. Have more questions? Let me know!

How Serial.available() Works

Serial.available() displays the serial port’s available bytes. This helps your Arduino sketch read serial data.

When Serial.available() is called, bytes are checked for read. Data is absent if it returns 0. If it returns a number larger than 0, it indicates bytes available.

If data is available, call to read bytes. As an example:

void setup() { Serial.begin(9600);

void loop() { if (Serial.available() > 0) { byte incoming =; // Process incoming byte }
This reads the first byte if data is available. Repeat to read more bytes up to Serial.available().

A typical mistake is calling without checking Serial.available(). Your sketch may hang waiting for data that may never arrive. Be sure to verify for data before reading!

To reassemble a message, you may receive numerous bytes of serial data. Before using data, read all bytes and arrange them into a message. You can do this:

String message; while (Serial.available() > 0) { message = (char); } // Complete the message
This will read and append bytes to the message string until all data is gone. Once complete, you can work with the message.

Serial.available() and let your Arduino sketch receive and process asynchronous serial data. With some parsing, you can establish basic serial protocols to control your Arduino from another device.

Some Common Serial.available() Uses

Serial.available() checks the serial port’s buffer for bytes. This helps read serial data without interrupting your program. Serial.availables() is often used:

Reading data only when available First check Serial.availables() to determine whether any data is ready before using, which will wait indefinitely. It saves time “waiting” for data when none is arriving.
Reading a set number of bytes To process a 5 byte message, use the following code: if (Serial.availables() >= 5) { byte message[5]; Serial.readBytes(message, 5); // Process message } This will only read the 5 bytes if there are enough available, preventing a timeout.

Full data reading Loop over the buffer to read all data:
While (Serial.availables() > 0) { byte incoming =; // Process incoming byte } Read bytes until all are read, emptying the serial buffer.

Avoiding buffer overruns Before reading more data than the buffer can hold, check Serial.availables() to avoid a buffer overrun issue.
Adaptive timing Serial.availables() can be looped to wait for a target number of bytes with a timeout. This lets you wait for data adaptively instead of fixedly.
As seen, Serial.availables() allows you additional control over serial data reading in projects. Use it properly to avoid timing difficulties, buffer overruns, and halted programs. I hope this clarifies this useful Arduino function! Any questions? Let me know.


That’s it for Serial.availables() and how to utilize it in your projects. What it does, why it matters, and crucial code snippets to make it work were covered. You may now impress your Arduino makerspace friends with your serial skills. Let your great ideas flow from mind to monitor! In 100 words, you’ve revealed this essential function’s mysteries. Try it in your next drawing and watch your work come to life one byte at a time. Your serial buffer has the power!

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